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The Critical Role of Level Monitoring in Ballast Tanks

Ballast tanks are compartments that are incorporated into the design of ships to maintain stability while at sea. A ballast system allows a vessel to pump water in and out of tanks to compensate for adjustments in cargo load, shallow draft areas or weather conditions.

Ballasts are not a modern invention, they have been utilized for centuries in various forms including solids such as sandbags and stones.

Today, liquids are used in the ballast tank which allows easier weight adjustment than the rocks and other solids previously utilized. Liquid ballast can include fresh water, salt water or brackish water in various ballast tanks.

A standard ballast system can include water intakes, strainers, pumps, distribution pipes, ballast water tanks, treatment system, discharge system, and all the valves, sensors, and controls to control and monitor the equipment.

Without a ballast system, several issues can arise including improper immersion level of the propeller. Without proper ballast, the propeller may not immerse fully into the water which can affect the efficiency of the ship’s engine.

Also, the vessel’s shear and torsion loads may overly stress the hull and structure, potentially causing bending and structural distortion. If cargo capacity is not reached, the ship may also list and trim without a balancing ballast system.

The ballast system addresses these issues, provides stability and reduces stresses on the ship’s hull. Ballasts help to keep the rudder properly submerged which increases the ship’s maneuverability. As a vessel uses its fuel supply, the ship’s weight is affected. The ballast system also serves to compensate this weight loss.

The flow profile within the distribution pipes must be closely monitored to ensure that there is enough fully developed turbulent flow to obtain an accurate measurement.

Other important factors include determining how much differential pressure the user needs to create, and ensuring that the created differential pressure properly matches the flow computer or transmitter. Another point to consider is how much of a pressure drop is acceptable in the flow stream.

Level Monitoring

Level transmitters, external remote indicators and network interfaces are incorporated into the ballast tank system which control the valves and ballast pumps for safe ballasting and de-ballasting operation.

KING-GAGE LP3 and LP2 systems utilize a capacity profile to correlate transmitter output to actual tank capacity. Application profiles, units of measurement and/or specific gravity values can be individually assigned to each tank as stored selections within the iButton Datapack memory.

In the ship’s engine room, several ballast pumps are used to pull sea water in from the main seawater line and also during the de-ballasting operation to discharge sea water to maintain proper stability and immersion.

The cargo control room houses the ballast tank level monitoring system, which controls the pump on/off operation as water levels trigger at specified sensor levels.

Below is a simplified overview showing level transmitters, external remote indicators and network interface to the ship’s control/management system.